How to Remove Rusted Bolts

We've all come across a nut that over time has rusted itself solid to the accompanying bolt. The rusted bolt is always tough to take off, but any DIYer with a level head and steady hand can tackle the challenge. The first rule is to invoke the patience of a Bonsai artist. Getting angry will put you at risk of making it worse. Much worse. Resist the temptation to force something that shouldn't be forced. Breaking a blind stud could mean hours of drilling out the busted shank. As with all projects, assess the situation and plan carefully using the following tips and tricks.

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Step 1: Is the Bolt Ready to Break?

The first thing you need to do is decide if the bolt is ready to break. Once a bolt yields, (stretched beyond its elastic limit), breaking is imminent. For example, exhaust manifold studs are notorious for corroding the shanks thin as twigs and just as easy to break.

Is the bolt actually rusted or does it have locking compound? Many factory bolts have thread locker applied. This can be softened with heat.

Is the bolt worth saving? A rusted fastener that has lost its tensile strength won't have the necessary clamping force to do its job. It false economy to even try and save a dead fastener. It may be easier to just break the bolt and replace it. Smaller fasteners such as body bolts and screws often can't be saved. Use locking pliers on J-nuts so they won't spin and simply break the bolt and discard.

Step 4: Select the Proper Tool

Select the proper tool. Open-end wrenches are most likely to round off the flats of a stuck nut. A 6-point box end is preferable to a 12-point for the same reason. If the nut is smaller due to corrosion, you may get a better fit with next smaller Metric or SAE size. For example a ½" socket (12.7mm) may be a better fit on rusted 13mm nut. Be careful; filing of the flats can fine-tune the fit. Cut the nuts off exhaust fasteners with an abrasive wheel mounted on a die grinder.

Step 5: Righty-Tighty, Lefty-Loosey

Are you turning it the correct way? Most mechanics learn the rhyme "Righty-Tighty, Lefty-Loosey" on day one, but you'd be surprised at how many still get their spatial directions confused when working in a reversed or upside down position. Note: Most threads are left hand loosen, but some ring gear bolts and old sixties Chrysler lug nuts can be backwards.

Step 6: Liquid Thread Looseners

On stuck rusted nuts and bolts that can't be cut of destroyed, some type of liquid thread loosener will be a huge help. There are many different brands to choose from but in most cases, testing has shown penetrating oil can reduce the torque required to overcome the rust bond by up to half or more. A home brew concoction of 50 percent Acetone and 50 percent ATF may work well in some cases, but be mindful of the fumes.

Step 7: Soak the Threads

Liberally soak the threads with penetrating oil. Whatever brand you use, you may need to repeat applications and possibly soak overnight. Remember, patience is key—it can save you hours spent drilling out a broken bolt.

Step 8: Getting More Leverage

A breaker bar or long handled ratchet will give more leverage. Use a steady, even pressure paying close attention to the feel or each turn. If the tension suddenly becomes soft or rubbery, you are either breaking the bolt or stripping the threads. Wear padded mechanics gloves to reduce skinned knuckles and the number of quarters put in the swearing jar.

Step 9: Heat Can Be Very Effective

If the nut is bonded to the bolt, you will need more serious techniques. Heat, carefully applied to one side of the nut, can expand it sufficiently to break the rust bond or melt locking compound. Be sure to first clean off all the penetrating oil and only use open flame in areas safe to do so.

Many modern cars have extensive amounts of plastic that can melt and catch fire if you are not vigilant. Because your vision is narrow through dark tinted safety glasses, have a spotter watching for telltale smoke or flames. Fireproof welder's blankets can be used to protect vital parts and paint from flame.

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I prefer using a very small oxyacetylene tip to concentrate heat in a tight area, but an inexpensive hardware store hand held propane torch can suffice if you have the room.

Step 10: Paraffin Acts as a Lubricant

My favorite trick for removing rusted NPT pipe plugs from cast iron is to heat the surrounding iron, then melt a candle on the threads. Paraffin will wick into the threads and act as a lubricant. Be sure to use a snug fitting, proper sized socket. In this example I used a special female square drive socket that fits the square on the pipe plug.

Step 11: The Tool of Last Resort

A pneumatic or electric impact gun should be the tool of last resort because it often simply breaks the bolt. Use the proper impact socket, wear gloves and safety glasses. Since these tools can be quite powerful, save them for larger nuts. If possible, use the impact on the nut side and hold the bolt with a wrench.